It runs on 24VDC, so if you energized it with the S3 power supply it would engage when you turned off your machine.Brake is spring actuated when no voltage is supplied to the unit. When current is supplied, the braking action is released.
If you put it on a relay and used the same relay to control your spindle you could make it disengage whenever the spindle was running.... I kind of like that idea. Not sure I like it $200 worth though.